!Crown Copyright 2012 AWE.
!
! This file is part of CloverLeaf.
!
! CloverLeaf is free software: you can redistribute it and/or modify it under 
! the terms of the GNU General Public License as published by the 
! Free Software Foundation, either version 3 of the License, or (at your option) 
! any later version.
!
! CloverLeaf is distributed in the hope that it will be useful, but 
! WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 
! FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more 
! details.
!
! You should have received a copy of the GNU General Public License along with 
! CloverLeaf. If not, see http://www.gnu.org/licenses/.

!>  @brief Fortran ideal gas kernel.
!>  @author Wayne Gaudin
!>  @details Calculates the pressure and sound speed for the mesh chunk using
!>  the ideal gas equation of state, with a fixed gamma of 1.4.

MODULE ideal_gas_kernel_module

CONTAINS

  SUBROUTINE ideal_gas_kernel(x_min,x_max,y_min,y_max,                &
                              density,                                &
                              energy,                                 &
                              pressure,                               &
                              soundspeed                              )

    IMPLICIT NONE

    INTEGER :: x_min,x_max,y_min,y_max
    REAL(KIND=8), DIMENSION(x_min-2:x_max+2,y_min-2:y_max+2) :: density
    REAL(KIND=8), DIMENSION(x_min-2:x_max+2,y_min-2:y_max+2) :: energy
    REAL(KIND=8), DIMENSION(x_min-2:x_max+2,y_min-2:y_max+2) :: pressure
    REAL(KIND=8), DIMENSION(x_min-2:x_max+2,y_min-2:y_max+2) :: soundspeed

    INTEGER :: j,k

    REAL(KIND=8) :: sound_speed_squared,v,pressurebyenergy,pressurebyvolume

    !$OMP PARALLEL
    !$OMP DO PRIVATE(v,pressurebyenergy,pressurebyvolume,sound_speed_squared)
    DO k=y_min,y_max
      DO j=x_min,x_max
        v=1.0_8/density(j,k)
        pressure(j,k)=(1.4_8-1.0_8)*density(j,k)*energy(j,k)
        pressurebyenergy=(1.4_8-1.0_8)*density(j,k)
        pressurebyvolume=-density(j,k)*pressure(j,k)
        sound_speed_squared=v*v*(pressure(j,k)*pressurebyenergy-pressurebyvolume)
        soundspeed(j,k)=SQRT(sound_speed_squared)
      ENDDO
    ENDDO
  !$OMP END DO
  !$OMP END PARALLEL

  END SUBROUTINE ideal_gas_kernel

END MODULE ideal_gas_kernel_module
